Planetary gear train of automatic transmission for vehicle

ABSTRACT

A planetary gear train of an automatic transmission for a vehicle may include: an input; an output; a first planetary gear set on the input including a first rotation element selectively connected to the input and selectively operated as a fixed element, a second rotation element selectively connected to the input and a third rotation element; a second planetary gear set on the output including a fourth rotation element connected to the second rotation element and selectively operated as a fixed element, a fifth rotation element connected to the third rotation element and directly connected to the output, and a sixth rotation element selectively connected to the input; four transfer gears; and frictional elements including clutches connecting the input and the rotation elements of the first and second planetary gear sets, and brakes connecting the rotation elements of the first and second planetary gear sets and a transmission housing.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority of Korean Patent ApplicationNumber 10-2012-0124113 filed Nov. 5, 2012, the entire contents of whichapplication is incorporated herein for all purposes by this reference.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to an automatic transmission for avehicle. More particularly, the present invention relates to a planetarygear train of an automatic transmission for a vehicle that can improvemountability and power delivery performance and reduce fuel consumption.

2. Description of Related Art

Recently, vehicle makers direct all their strength to improve fueleconomy due to worldwide high oil prices and strengthen of exhaust gasregulations.

Improvement of fuel economy may be achieved by multi-shift mechanismrealizing greater number of shift speeds in an automatic transmission.Typically, a planetary gear train is realized by combining a pluralityof planetary gear sets and friction elements.

It is well known that when a planetary gear train realizes a greaternumber of shift speeds, speed ratios of the planetary gear train can bemore optimally designed, and therefore a vehicle can have economicalfuel mileage and better performance. For that reason, the planetary geartrain that is able to realize more shift speeds is under continuousinvestigation.

Though achieving the same number of speeds, the planetary gear train hasa different operating mechanism according to a connection betweenrotation elements (i.e., sun gear, planet carrier, and ring gear). Inaddition, the planetary gear train has different features such adurability, power delivery efficiency, and size depend on the layoutthereof. Therefore, designs for a combining structure of a gear trainare also under continuous investigation.

If the number of shift-speeds, however, increases, the number ofcomponents in the automatic transmission also increases. Therefore,mountability, cost, weight and power delivery efficiency may bedeteriorated.

Particularly, since the planetary gear train having a number ofcomponents is hard to be mounted in a front wheel drive vehicle,researches for minimizing the number of components have been developed.

The information disclosed in this Background section is only forenhancement of understanding of the general background of the inventionand should not be taken as an acknowledgement or any form of suggestionthat this information forms the prior art already known to a personskilled in the art.

BRIEF SUMMARY

Various aspects of the present invention provide for a planetary geartrain of an automatic transmission for a vehicle having advantages ofimproving mountability by shortening a length thereof and reducing thenumber of components as a consequence of achieving nine forward speedsand one reverse speed by disposing two planetary gear sets separately onan input shaft and an output shaft disposed in parallel and connectingrotation elements of the planetary gear sets through a plurality ofexternally-meshed gears.

In addition, the present invention has been made in an effort to providea planetary gear train of an automatic transmission for a vehicle havingfurther advantages of enabling of setting optimum gear ratios due toease of changing gear ratios by using a plurality of externally-meshedgears, and accordingly improving power delivery performance and fueleconomy.

A planetary gear train of an automatic transmission for a vehicleaccording to one aspect of the present invention may include: an inputshaft receiving torque of an engine; an output shaft disposed inparallel with the input shaft with a predetermined distance andoutputting changed torque; a first planetary gear set disposed on theinput shaft, and including a first rotation element selectivelyconnected to the input shaft and selectively operated as a fixedelement, a second rotation element selectively connected to the inputshaft, and a third rotation element; a second planetary gear setdisposed on the output shaft, and including a fourth rotation elementconnected to the second rotation element through an externally-meshedgear and selectively operated as a fixed element, a fifth rotationelement connected to the third rotation element through anexternally-meshed gear and directly connected to the output shaft, and asixth rotation element selectively connected to the input shaft throughtwo externally-meshed gears having different gear ratios; four transfergears forming the externally-meshed gears; and frictional elementsincluding clutches connecting the input shaft and the rotation elementsof the first and second planetary gear sets and brakes connecting therotation elements of the first and second planetary gear sets and atransmission housing.

The first planetary gear set may be a single pinion planetary gear setincluding a first sun gear being the first rotation element, a firstplanet carrier being the second rotation element, and a first ring gearbeing the third rotation element, and the second planetary gear set maybe a single pinion planetary gear set and including a second sun gearbeing the fourth rotation element, a second planet carrier being thefifth rotation element, and a second ring gear being the sixth rotationelement.

The four transfer gears may include: a first transfer gear connectingthe second rotation element with the fourth rotation element; a secondtransfer gear connecting the third rotation element with the fifthrotation element; a third transfer gear connecting the input shaft withthe sixth rotation element; and a fourth transfer gear connecting theinput shaft with the sixth rotation element.

A gear ratio of the third transfer gear may be different from that ofthe fourth transfer gear.

The frictional elements may include: a first clutch selectivelyconnecting the third transfer gear with the sixth rotation element; asecond clutch selectively connecting the input shaft with the firstrotation element; a third clutch selectively connecting the secondrotation element with the input shaft and the fourth transfer gear; afourth clutch selectively connecting the fourth transfer gear with thesixth rotation element; a first brake selectively connecting the fourthrotation element with the transmission housing; and a second brakeselectively connecting the first rotation element with the transmissionhousing.

The first clutch and the first brake may be operated at a first forwardspeed, the first clutch and the second brake may be operated at a secondforward speed, the first clutch and the second clutch may be operated ata third forward speed, the first clutch and the third clutch may beoperated at a fourth forward speed, the second clutch and the thirdclutch may be operated at a fifth forward speed, the third clutch andthe second brake may be operated at a sixth forward speed, the thirdclutch and the fourth clutch may be operated at a seventh forward speed,the fourth clutch and the second brake may be operated at an eighthforward speed, the second clutch and the fourth clutch may be operatedat a ninth forward speed, and the second clutch and the first brake maybe operated at a reverse speed.

The frictional elements may include: a first clutch selectivelyconnecting the third transfer gear with the sixth rotation element; asecond clutch selectively connecting the input shaft with the firstrotation element; a third clutch selectively connecting the secondrotation element with the input shaft and the fourth transfer gear; afourth clutch selectively connecting the fourth transfer gear with thesixth rotation element; a first brake selectively connecting the secondrotation element with the transmission housing; and a second brakeselectively connecting the first rotation element with the transmissionhousing.

The frictional elements may include: a first clutch selectivelyconnecting the third transfer gear with the sixth rotation element; asecond clutch selectively connecting the input shaft with the firstrotation element; a third clutch selectively connecting the secondrotation element with the fourth transfer gear; a fourth clutchselectively connecting the input shaft with the fourth transfer gear; afirst brake selectively connecting the fourth rotation element with thetransmission housing; and a second brake selectively connecting thefirst rotation element with the transmission housing.

The frictional elements may include: a first clutch selectivelyconnecting the input shaft with the third transfer gear; a second clutchselectively connecting the input shaft with the first rotation element;a third clutch selectively connecting the second rotation element withthe input shaft and the fourth transfer gear; a fourth clutchselectively connecting the fourth transfer gear with the sixth rotationelement; a first brake selectively connecting the fourth rotationelement with the transmission housing; and a second brake selectivelyconnecting the first rotation element with the transmission housing.

The first planetary gear set may be a single pinion planetary gear trainincluding a first sun gear being the first rotation element, a firstplanet carrier being the second rotation element, and a first ring gearbeing the third rotation element, and the second planetary gear set maybe a double pinion planetary gear set including a second sun gear beingthe fourth rotation element, a second ring gear being the fifth rotationelement, and a second planet carrier being the sixth rotation element.

A planetary gear train of an automatic transmission for a vehicleaccording to another aspect of the present invention may include: aninput shaft receiving torque of an engine; an output shaft disposed inparallel with the input shaft with a predetermined distance andoutputting changed torque; a first planetary gear set disposed on theinput shaft, and including a first rotation element selectivelyconnected to the input shaft and selectively operated as a fixedelement, a second rotation element selectively connected to the inputshaft, and a third rotation element; a second planetary gear setdisposed on the output shaft, and including a fourth rotation elementconnected to the second rotation element and selectively operated as afixed element, a fifth rotation element connected to the third rotationelement and directly connected to the output shaft, and a sixth rotationelement selectively connected to the input shaft through two pathshaving different gear ratios; a first transfer gear connecting thesecond rotation element with the fourth rotation element; a secondtransfer gear connecting the third rotation element with the fifthrotation element; a third transfer gear connecting the input shaft withthe sixth rotation element; a fourth transfer gear connecting the inputshaft with the sixth rotation element; and frictional elements includingclutches connecting the input shaft and the rotation elements of thefirst and second planetary gear sets and brakes connecting the rotationelements of the first and second planetary gear sets and a transmissionhousing.

A gear ratio of the third transfer gear may be different from that ofthe fourth transfer gear.

The first planetary gear set may be a single pinion planetary gear setincluding a first sun gear being the first rotation element, a firstplanet carrier being the second rotation element, and a first ring gearbeing the third rotation element, and the second planetary gear set maybe a single pinion planetary gear set and including a second sun gearbeing the fourth rotation element, a second planet carrier being thefifth rotation element, and a second ring gear being the sixth rotationelement.

The first planetary gear set may be a single pinion planetary gear trainincluding a first sun gear being the first rotation element, a firstplanet carrier being the second rotation element, and a first ring gearbeing the third rotation element, and the second planetary gear set maybe a double pinion planetary gear set including a second sun gear beingthe fourth rotation element, a second ring gear being the fifth rotationelement, and a second planet carrier being the sixth rotation element.

The frictional elements may include: a first clutch selectivelyconnecting the third transfer gear with the sixth rotation element; asecond clutch selectively connecting the input shaft with the firstrotation element; a third clutch selectively connecting the secondrotation element with the input shaft and the fourth transfer gear; afourth clutch selectively connecting the fourth transfer gear with thesixth rotation element; a first brake selectively connecting the fourthrotation element with the transmission housing; and a second brakeselectively connecting the first rotation element with the transmissionhousing.

The frictional elements may include: a first clutch selectivelyconnecting the third transfer gear with the sixth rotation element; asecond clutch selectively connecting the input shaft with the firstrotation element; a third clutch selectively connecting the secondrotation element with the input shaft and the fourth transfer gear; afourth clutch selectively connecting the fourth transfer gear with thesixth rotation element; a first brake selectively connecting the secondrotation element with the transmission housing; and a second brakeselectively connecting the first rotation element with the transmissionhousing.

The frictional elements may include: a first clutch selectivelyconnecting the third transfer gear with the sixth rotation element; asecond clutch selectively connecting the input shaft with the firstrotation element; a third clutch selectively connecting the secondrotation element with the fourth transfer gear; a fourth clutchselectively connecting the input shaft with the fourth transfer gear; afirst brake selectively connecting the fourth rotation element with thetransmission housing; and a second brake selectively connecting thefirst rotation element with the transmission housing.

The frictional elements may include: a first clutch selectivelyconnecting the input shaft with the third transfer gear; a second clutchselectively connecting the input shaft with the first rotation element;a third clutch selectively connecting the second rotation element withthe input shaft and the fourth transfer gear; a fourth clutchselectively connecting the fourth transfer gear with the sixth rotationelement; a first brake selectively connecting the fourth rotationelement with the transmission housing; and a second brake selectivelyconnecting the first rotation element with the transmission housing.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description, which together serve to explaincertain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an exemplary planetary gear trainaccording to the present invention.

FIG. 2 is an operational chart of friction elements at each shift-speedapplied to the planetary gear train of FIG. 1.

FIG. 3A is a lever diagram of a planetary gear train according to theplanetary gear train of FIG. 1 at the first forward speed.

FIG. 3B is a lever diagram of a planetary gear train according to theplanetary gear train of FIG. 1 at the second forward speed.

FIG. 3C is a lever diagram of a planetary gear train according to theplanetary gear train of FIG. 1 at the third forward speed.

FIG. 3D is a lever diagram of a planetary gear train according to theplanetary gear train of FIG. 1 at the fourth forward speed.

FIG. 3E is a lever diagram of a planetary gear train according to theplanetary gear train of FIG. 1 at the fifth forward speed.

FIG. 3F is a lever diagram of a planetary gear train according to theplanetary gear train of FIG. 1 at the sixth forward speed.

FIG. 3G is a lever diagram of a planetary gear train according to theplanetary gear train of FIG. 1 at the seventh forward speed.

FIG. 3H is a lever diagram of a planetary gear train according to theplanetary gear train of FIG. 1 at the eighth forward speed.

FIG. 3I is a lever diagram of a planetary gear train according to theplanetary gear train of FIG. 1 at the ninth forward speed.

FIG. 3J is a lever diagram of a planetary gear train according to theplanetary gear train of FIG. 1 at the reverse speed.

FIG. 4 is a schematic diagram of an exemplary planetary gear trainaccording to the present invention.

FIG. 5 is a schematic diagram of an exemplary planetary gear trainaccording to the present invention.

FIG. 6 is a schematic diagram of an exemplary planetary gear trainaccording to the present invention.

FIG. 7 is a schematic diagram of an exemplary planetary gear trainaccording to the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying drawings and described below. While the invention(s) willbe described in conjunction with exemplary embodiments, it will beunderstood that present description is not intended to limit theinvention(s) to those exemplary embodiments. On the contrary, theinvention(s) is/are intended to cover not only the exemplaryembodiments, but also various alternatives, modifications, equivalentsand other embodiments, which may be included within the spirit and scopeof the invention as defined by the appended claims.

Description of components that are not necessary for explaining theillustrated embodiments will be omitted, and the same constituentelements are denoted by the same reference numerals in thisspecification.

In the detailed description, ordinal numbers are used for distinguishingconstituent elements having the same terms, and have no specificmeanings.

FIG. 1 is a schematic diagram of a planetary gear train according tovarious embodiments of the present invention.

Referring to FIG. 1, a planetary gear train according to variousembodiments of the present invention includes a first planetary gear setPG1 disposed on an input shaft IS, a second planetary gear set PG2disposed on an output shaft OS disposed in parallel with the input shaftIS, four transfer gears TF1, TF2, TF3, and TF4, and frictional elementsconsisting of four clutches C1, C2, C3, and C4 and two brakes B1 and B2.

Therefore, torque input from the input shaft IS is converted into nineforward speeds and one reverse speed by cooperation of the first andsecond planetary gear sets PG1 and PG2, and then is output through theoutput shaft OS.

The input shaft IS is an input member, and torque from a crankshaft ofthe engine is changed through a torque converter and is then input tothe input shaft IS.

The output shaft OS is an output member and transmits driving torque toa driving wheel through a differential apparatus.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1 being a first rotation element N1, afirst planet carrier PC1 rotatably supporting a first pinion P1externally meshed with the first sun gear S1 and being a second rotationelement N2, and a first ring gear R1 internally meshed with the firstpinion P1 and being a third rotation element N3.

The second planetary gear set PG2 is a single pinion planetary gear set,and includes a second sun gear S2 being a fourth rotation element N4, asecond planet carrier PC2 rotatably supporting a second pinion P2externally meshed with the second sun gear S2 and being a fifth rotationelement N5, and a second ring gear R2 internally meshed with the secondpinion P2 and being a sixth rotation element N6.

Two rotation elements of the first planetary gear set PG1 is selectivelyconnected to the input shaft IS, three rotation elements of the secondplanetary gear set PG2 is connected to the input shaft IS and tworotation elements of the first planetary gear set PG1 through first,second, third, and fourth transfer gears TF1, TF2, TF3, and TF4, and anyone rotation element of the second planetary gear set PG2 is directlyconnected to the output shaft OS.

The first, second, third, and fourth transfer gears TF1, TF2, TF3, andTF4 respectively have first, second, third, and fourth transfer drivegears TF1 a, TF2 a, TF3 a, and TF4 a and first, second, third, andfourth transfer driven gears TF1 b, TF2 b, TF3 b, and TF4 b externallymeshed with each other.

The first transfer gear TF1 connects the second rotation element N2 withthe fourth rotation element N4.

The second transfer gear TF2 connects the third rotation element N3 withthe fifth rotation element N5.

The third transfer gear TF3 connects the input shaft IS with the sixthrotation element N6.

The fourth transfer gear TF4 connects the input shaft IS with the sixthrotation element N6.

Therefore, the rotation elements (including the first shaft IS1)connected with each other through the first, second, third, and fourthtransfer gears TF1, TF2, TF3, and TF4 are rotated in opposite directionto each other according to gear ratios of the first, second, third, andfourth transfer gears TF1, TF2, TF3, and TF4.

In addition, four clutches C1, C2, C3, and C4 and two brakes B1 and B2selectively connecting the selected rotation elements with the inputshaft IS and the transmission housing H are disposed as follows.

The first clutch C1 selectively connects the third transfer gear TF3with the sixth rotation element N6.

The second clutch C2 selectively connects the input shaft IS with thefirst rotation element N1.

The third clutch C3 selectively connects the second rotation elementwith the input shaft IS and the fourth transfer gear TF4.

The fourth clutch C4 selectively connects the fourth transfer gear TF4with the sixth rotation element N6.

The first brake B1 selectively connects the fourth rotation element N4with the transmission housing H.

The second brake B2 selectively connects the first rotation element N1with the transmission housing H.

Both of the first clutch C1 and the fourth clutch C4 selectively connectthe input shaft IS with the sixth rotation element N6, but rotationspeeds transmitted to the sixth rotation element N6 through the firstclutch C1 and the fourth clutch C4 are different from each other sincethe gear ratio of the third transfer gear TF3 differs from the gearratio of the fourth transfer gear TF4.

The frictional elements consisting of the first, second, third, andfourth clutches C1, C2, C3, and C4 and the first and second brakes B1and B2 are conventional multi-plate friction elements of wet type thatare operated by hydraulic pressure.

FIG. 2 is an operational chart of friction elements at each shift-speedapplied to a planetary gear train according to the planetary gear trainof FIG. 1.

As shown in FIG. 2, two frictional elements are operated at eachshift-speed in the planetary gear train according to various embodimentsof the present invention.

The first clutch C1 and the first brake B1 are operated at a firstforward speed 1ST.

The first clutch C1 and the second brake B2 are operated at a secondforward speed 2ND.

The first clutch C1 and the second clutch C2 are operated at a thirdforward speed 3RD.

The first clutch C1 and the third clutch C3 are operated at a fourthforward speed 4TH.

The second clutch C2 and the third clutch C3 are operated at a fifthforward speed 5TH.

The third clutch C3 and the second brake B2 are operated at a sixthforward speed 6TH.

The third clutch C3 and the fourth clutch C4 are operated at a seventhforward speed 7TH.

The fourth clutch C4 and the second brake B2 are operated at an eighthforward speed 8TH.

The second clutch C2 and the fourth clutch C4 are operated at a ninthforward speed 9TH.

The second clutch C2 and the first brake B1 are operated at a reversespeed Rev.

FIG. 3A to FIG. 3J are lever diagrams of a planetary gear trainaccording to the planetary gear train of FIG. 1, and illustrate shiftprocesses of the planetary gear train according to the planetary geartrain of FIG. 1 by lever analysis method.

Referring to FIG. 3A to FIG. 3J, three vertical lines of the firstplanetary gear set PG2 are set as the first, second, and third rotationelements N1, N2, and N3, and three vertical lines of the secondplanetary gear set PG2 are set as the fourth, fifth, and sixth rotationelements N4, N5, and N6.

A middle horizontal line represents a rotation speed of “0”, upperhorizontal lines represent positive rotation speeds and lower horizontallines represent negative rotation speeds.

“−” means that rotational elements are rotated in an opposite directionto the rotation direction of the engine. It is because the input shaftIS and the rotation elements of the first planetary gear set PG1 areexternally meshed through the first, second, third, and fourth transfergears TF1, TF2, TF3, and TF4 without an idling gear.

In addition, distances between the vertical lines of the first andsecond planetary gear sets PG1 and PG2 are set according to gear ratios(teeth number of a sun gear/teeth number of a ring gear).

Hereinafter, referring to FIG. 2 and FIG. 3A to FIG. 3J, the shiftprocesses of the planetary gear train according to the planetary geartrain of FIG. 1 will be described in detail.

First Forward Speed

Referring to FIG. 2, the first clutch C1 and the first brake B1 areoperated at the first forward speed 1ST.

As shown in FIG. 3A, in a state that the third rotation element N3 isconnected to the fifth rotation element N5 through the second transfergear TF2 and the second rotation element N2 is connected to the fourthrotation element N4 through the first transfer gear TF1, the firstclutch C1 and the first brake B1 are operated.

Therefore, the rotation speed of the input shaft IS is convertedaccording to the gear ratio of the third transfer gear TF3 and is theninput to the sixth rotation element N6 as an inverse rotation speed byoperation of the first clutch C1. In addition, the second and fourthrotation elements N2 and N4 are operated as the fixed elements byoperation of the first brake B1.

Therefore, the rotation elements of the first planetary gear set PG1form a first speed line T1 and the rotation elements of the secondplanetary gear set PG2 form a first shift line SP1 by cooperation of thefirst planetary gear set PG1 and the second planetary gear set PG2.Therefore, D1 is output through the fifth rotation element N5 that isthe output element.

Second Forward Speed

The first brake B1 that was operated at the first forward speed 1ST isreleased and the second brake B2 is operated at the second forward speed2ND.

As shown in FIG. 3B, in a state that the third rotation element N3 isconnected to the fifth rotation element N5 through the second transfergear TF2 and the second rotation element N2 is connected to the fourthrotation element N4 through the first transfer gear TF1, the firstclutch C1 and the second brake B2 are operated.

Therefore, the rotation speed of the input shaft IS is convertedaccording to the gear ratio of the third transfer gear TF3 and is theninput to the sixth rotation element N6 as an inverse rotation speed byoperation of the first clutch C1. In addition, the first rotationelement N1 is operated as the fixed element by operation of the secondbrake B2.

Therefore, the rotation elements of the first planetary gear set PG1form a second speed line T2 and the rotation elements of the secondplanetary gear set PG2 form a second shift line SP2 by cooperation ofthe first planetary gear set PG1 and the second planetary gear set PG2.Therefore, D2 is output through the fifth rotation element N5 that isthe output element.

Third Forward Speed

The second brake B2 that was operated at the second forward speed 2ND isreleased and the second clutch C2 is operated at the third forward speed3RD.

As shown in FIG. 3C, in a state that the third rotation element N3 isconnected to the fifth rotation element N5 through the second transfergear TF2 and the second rotation element N2 is connected to the fourthrotation element N4 through the first transfer gear TF1, the firstclutch C1 and the second clutch C2 are operated.

Therefore, the rotation speed of the input shaft IS is convertedaccording to the gear ratio of the third transfer gear TF3 and is theninput to the sixth rotation element N6 as an inverse rotation speed byoperation of the first clutch C1. In addition, the rotation speed of theinput shaft IS is directly input to the first rotation element N1 byoperation of the second clutch C2.

Therefore, the rotation elements of the first planetary gear set PG1form a third speed line T3 and the rotation elements of the secondplanetary gear set PG2 form a third shift line SP3 by cooperation of thefirst planetary gear set PG1 and the second planetary gear set PG2.Therefore, D3 is output through the fifth rotation element N5 that isthe output element.

Fourth Forward Speed

The second clutch C2 that was operated at the third forward speed 3RD isreleased and the third clutch C3 is operated at the fourth forward speed4TH.

As shown in FIG. 3D, in a state that the third rotation element N3 isconnected to the fifth rotation element N5 through the second transfergear TF2 and the second rotation element N2 is connected to the fourthrotation element N4 through the first transfer gear TF1, the firstclutch C1 and the third clutch C3 are operated.

Therefore, the rotation speed of the input shaft IS is convertedaccording to the gear ratio of the third transfer gear TF3 and is theninput to the sixth rotation element N6 as an inverse rotation speed byoperation of the first clutch C1. In addition, the rotation speed of theinput shaft IS is directly input to the second rotation element N2 byoperation of the third clutch C3.

Therefore, the rotation elements of the first planetary gear set PG1form a fourth speed line T4 and the rotation elements of the secondplanetary gear set PG2 form a fourth shift line SP4 by cooperation ofthe first planetary gear set PG1 and the second planetary gear set PG2.Therefore, D4 is output through the fifth rotation element N5 that isthe output element.

Fifth Forward Speed

The first clutch C1 that was operated at the fourth forward speed 4TH isreleased and the second clutch C2 is operated at the fifth forward speed5TH.

As shown in FIG. 3E, in a state that the third rotation element N3 isconnected to the fifth rotation element N5 through the second transfergear TF2 and the second rotation element N2 is connected to the fourthrotation element N4 through the first transfer gear TF1, the secondclutch C2 and the third clutch C3 are operated.

Therefore, the rotation speed of the input shaft IS is directly input tothe first rotation element N1 by operation of the second clutch C2 andis directly input to the second rotation element N2 by operation of thethird clutch C3 such that the first planetary gear set PG1 becomes adirect-coupling state.

Therefore, the rotation elements of the first planetary gear set PG1form a fifth speed line T5 and the rotation elements of the secondplanetary gear set PG2 form a fifth shift line SP5 by cooperation of thefirst planetary gear set PG1 and the second planetary gear set PG2.Therefore, D5 is output through the fifth rotation element N5 that isthe output element.

Sixth Forward Speed

The second clutch C1 that was operated at the fifth forward speed 5TH isreleased and the second brake B2 is operated at the sixth forward speed6TH.

As shown in FIG. 3F, in a state that the third rotation element N3 isconnected to the fifth rotation element N5 through the second transfergear TF2 and the second rotation element N2 is connected to the fourthrotation element N4 through the first transfer gear TF1, the thirdclutch C3 and the second brake B2 are operated.

Therefore, the rotation speed of the input shaft IS is directly input tothe second rotation element N2 by operation of the third clutch C3 andthe first rotation element N1 is operated as the fixed element byoperation of the second brake B2.

Therefore, the rotation elements of the first planetary gear set PG1form a sixth speed line T6 and the rotation elements of the secondplanetary gear set PG2 form a sixth shift line SP6 by cooperation of thefirst planetary gear set PG1 and the second planetary gear set PG2.Therefore, D6 is output through the fifth rotation element N5 that isthe output element.

Seventh Forward Speed

The second brake B2 that was operated at the sixth forward speed 6TH isreleased and the fourth clutch C4 is operated at the seventh forwardspeed 7TH.

As shown in FIG. 3G, in a state that the third rotation element N3 isconnected to the fifth rotation element N5 through the second transfergear TF2 and the second rotation element N2 is connected to the fourthrotation element N4 through the first transfer gear TF1, the thirdclutch C3 and the fourth clutch C4 are operated.

Therefore, the rotation speed of the input shaft IS is directly input tothe second rotation element N2 by operation of the third clutch C3, andis converted according to the gear ratio of the fourth transfer gear TF4and is then input to the sixth rotation element N6 as an inverserotation speed by operation of the fourth clutch C4.

Therefore, the rotation elements of the first planetary gear set PG1form a seventh speed line T7 and the rotation elements of the secondplanetary gear set PG2 form a seventh shift line SP7 by cooperation ofthe first planetary gear set PG1 and the second planetary gear set PG2.Therefore, D7 is output through the fifth rotation element N5 that isthe output element.

Eighth Forward Speed

The third clutch C3 that was operated at the seventh forward speed 7THis released and the second brake B2 is operated at the eighth forwardspeed 8TH.

As shown in FIG. 3H, in a state that the third rotation element N3 isconnected to the fifth rotation element N5 through the second transfergear TF2 and the second rotation element N2 is connected to the fourthrotation element N4 through the first transfer gear TF1, the fourthclutch C4 and the second brake B2 are operated.

Therefore, the rotation speed of the input shaft IS is convertedaccording to the gear ration of the fourth transfer gear TF4 and is theninput to the sixth rotation element N6 as an inverse rotation speed byoperation of the fourth clutch C4. In addition, the first rotationelement N1 is operated as the fixed element by operation of the secondbrake B2.

Therefore, the rotation elements of the first planetary gear set PG1form an eighth speed line T8 and the rotation elements of the secondplanetary gear set PG2 form an eighth shift line SP8 by cooperation ofthe first planetary gear set PG1 and the second planetary gear set PG2.Therefore, D8 is output through the fifth rotation element N5 that isthe output element.

Ninth Forward Speed

The second brake B2 that was operated at the eighth forward speed 8TH isreleased and the second clutch C2 is operated at the ninth forward speed9TH.

As shown in FIG. 3I, in a state that the third rotation element N3 isconnected to the fifth rotation element N5 through the second transfergear TF2 and the second rotation element N2 is connected to the fourthrotation element N4 through the first transfer gear TF1, the fourthclutch C4 and the second clutch C2 are operated.

Therefore, the rotation speed of the input shaft IS is directly input tothe first rotation element N1 by operation of the second clutch C2, andis converted according to the gear ratio of the fourth transfer gear TF4and is then input to the sixth rotation element N6 as an inverserotation speed by operation of the fourth clutch C4.

Therefore, the rotation elements of the first planetary gear set PG1form a ninth speed line T9 and the rotation elements of the secondplanetary gear set PG2 form a ninth shift line SP9 by cooperation of thefirst planetary gear set PG1 and the second planetary gear set PG2.Therefore, D9 is output through the fifth rotation element N5 that isthe output element.

Reverse Speed

As shown in FIG. 2, the second clutch C2 and the first brake B1 areoperated at the reverse speed Rev.

As shown in FIG. 3J, in a state that the third rotation element N3 isconnected to the fifth rotation element N5 through the second transfergear TF2 and the second rotation element N2 is connected to the fourthrotation element N4 through the first transfer gear TF1, the secondclutch C2 and the first brake B1 are operated.

Therefore, the rotation speed of the input shaft IS is directly input tothe first rotation element N1 by operation of the second clutch C2, andthe second rotation element N2 and the fourth rotation element N4 areoperated as the fixed elements by operation of the first brake B1.

Therefore, the rotation elements of the first planetary gear set PG1form a reverse speed line Tr and the rotation elements of the secondplanetary gear set PG2 form a reverse shift line RS by cooperation ofthe first planetary gear set PG1 and the second planetary gear set PG2.Therefore, REV is output through the fifth rotation element N5 that isthe output element.

As described above, the planetary gear train according to the planetarygear train of FIG. 1 can achieve nine forward speeds and one reversespeed by combining two planetary gear sets PG1 and PG2 being the simpleplanetary gear sets, four transfer gears TF1, TF2, TF3, and TF4 beingthe externally-meshed gears and six frictional elements C1, C2, C3, C4,B1, and B2.

In addition, optimum gear ratios may be set due to ease of changing gearratios by using four transfer gears being externally-meshed gears aswell as the planetary gear sets. Since gear ratios can be changedaccording to target performance, starting performance, power deliveryperformance and fuel economy may be improved. Therefore, a start-upclutch instead of a torque converter may be used.

In addition, two friction elements are operated at each shift-speed andone friction element is released and another friction element isoperated so as to shift to a neighboring shift-speed. Therefore, shiftcontrol condition is fully satisfied.

FIG. 4 is a schematic diagram of a planetary gear train according tovarious embodiments.

Referring to FIG. 4, the first brake B1 is disposed between the fourthrotation element N4 and the transmission housing H in the planetary geartrain of FIG. 1, but the first brake B1 is disposed between the secondrotation element N2 and the transmission housing H in the planetary geartrain of FIG. 4.

Since functions of the planetary gear train of FIG. 4 are the same asthose of the planetary gear train of FIG. 1 except the position of thefirst brake B1, detailed description thereof will be omitted.

FIG. 5 is a schematic diagram of a planetary gear train according tovarious embodiments of the present invention.

Referring to FIG. 5, the fourth clutch C4 is disposed between the fourthtransfer gear TF4 and the sixth rotation element N6 in the planetarygear train of FIG. 1, but the fourth clutch C4 is disposed between theinput shaft IS and the fourth transfer gear TF4 in the planetary geartrain of FIG. 5.

Therefore, the third clutch C3 is disposed between the second rotationelement N2 and the fourth transfer gear TF4 and the fourth clutch C4 isdisposed between the input shaft IS and the fourth transfer gear TF4.

Since functions of the planetary gear train of FIG. 5 are the same asthose of the planetary gear train of FIG. 1 except the position of thefourth clutch C4, detailed description thereof will be omitted.

FIG. 6 is a schematic diagram of a planetary gear train according tovarious embodiments of the present invention.

Referring to FIG. 6, the first clutch C1 is disposed between the thirdtransfer gear TF3 and the sixth rotation element N6 in the planetarygear train of FIG. 1, but the first clutch C1 is disposed between theinput shaft IS and the third transfer gear TF3 in the planetary geartrain of FIG. 6.

Since functions of the planetary gear train of FIG. 6 are the same asthose of the planetary gear train of FIG. 1 except the position of thefirst clutch C1, detailed description thereof will be omitted.

FIG. 7 is a schematic diagram of a planetary gear train according tovarious embodiments of the present invention.

Referring to FIG. 7, the second planetary gear set PG2 is the singlepinion planetary gear set in the planetary gear train of FIG. 1, but thesecond planetary gear set PG2 is a double pinion planetary gear set inthe planetary gear train of FIG. 7.

Therefore, the fifth rotation element N5 is changed from the secondplanet carrier PC2 to the second ring gear R2 and the sixth rotationelement N6 is changed from the second ring gear R2 to the second planetcarrier PC2.

Since functions of the planetary gear train of FIG. 7 are the same asthose of the planetary gear train of FIG. 1 except the rotation elementsconsisting of the fifth and sixth rotation elements N5 and N6, detaileddescription thereof will be omitted.

Nine forward speeds and one reverse speed can be achieved by combiningtwo planetary gear sets being the simple planetary gear sets, fourtransfer gears and six frictional elements.

In addition, since two planetary gear sets are disposed separately onthe input shaft and the output shaft disposed in parallel with apredetermined distance, a length thereof may be reduced and mountabilitymay be improved.

In addition, optimum gear ratios may be set due to ease of changing gearratios by using four external-meshing gears as well as the planetarygear sets. Since gear ratios can be changed according to targetperformance, starting performance, power delivery performance, and fueleconomy may be improved. Therefore, a start-up clutch instead of atorque converter may be used.

In addition, two friction elements are operated at each shift-speed, andone friction element is released and another friction element isoperated so as to shift to a neighboring shift-speed. Therefore, shiftcontrol condition is fully satisfied.

For convenience in explanation and accurate definition in the appendedclaims, the terms upper or lower, and etc. are used to describe featuresof the exemplary embodiments with reference to the positions of suchfeatures as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. The exemplary embodiments were chosen and described in orderto explain certain principles of the invention and their practicalapplication, to thereby enable others skilled in the art to make andutilize various exemplary embodiments of the present invention, as wellas various alternatives and modifications thereof. It is intended thatthe scope of the invention be defined by the Claims appended hereto andtheir equivalents.

What is claimed is:
 1. A planetary gear train of an automatictransmission for a vehicle, comprising: an input shaft receiving torqueof an engine; an output shaft disposed in parallel with the input shaftat a predetermined distance from the input shaft and outputting changedtorque; a first planetary gear set disposed on the input shaft andincluding a first rotation element selectively connected to the inputshaft and selectively operated as a fixed element, a second rotationelement selectively connected to the input shaft, and a third rotationelement; a second planetary gear set disposed on the output shaft, andincluding a fourth rotation element connected to the second rotationelement through a first externally-meshed gear and selectively operatedas a fixed element, a fifth rotation element connected to the thirdrotation element through a second externally-meshed gear and directlyconnected to the output shaft, and a sixth rotation element selectivelyconnected to the input shaft through third and fourth externally-meshedgears, wherein a gear ratio of the third externally-meshed gear isdifferent from that of the fourth externally-meshed gear; four transfergears forming the first, second, third and fourth externally-meshedgears; and frictional elements including clutches connecting the inputshaft and the rotation elements of the first and second planetary gearsets and brakes connecting the rotation elements of the first and secondplanetary gear sets and a transmission housing, wherein the firstplanetary gear set is a single pinion planetary gear set including afirst sun gear being the first rotation element, a first planet carrierbeing the second rotation element, and a first ring gear being the thirdrotation element, and the second planetary gear set is a single pinionplanetary gear set and including a second sun gear being the fourthrotation element, a second planet carrier being the fifth rotationelement, and a second ring gear being the sixth rotation element.
 2. Theplanetary gear train of claim 1, wherein the four transfer gearscomprise: a first transfer gear connecting the second rotation elementwith the fourth rotation element; a second transfer gear connecting thethird rotation element with the fifth rotation element; a third transfergear connecting the input shaft with the sixth rotation element; and afourth transfer gear connecting the input shaft with the sixth rotationelement.
 3. The planetary gear train of claim 2, wherein a gear ratio ofthe third transfer gear is different from that of the fourth transfergear.
 4. The planetary gear train of claim 2, wherein the frictionalelements comprise: a first clutch selectively connecting the thirdtransfer gear with the sixth rotation element; a second clutchselectively connecting the input shaft with the first rotation element;a third clutch selectively connecting the second rotation element withthe input shaft and the fourth transfer gear; a fourth clutchselectively connecting the fourth transfer gear with the sixth rotationelement; a first brake selectively connecting the fourth rotationelement with the transmission housing; and a second brake selectivelyconnecting the first rotation element with the transmission housing. 5.The planetary gear train of claim 4, wherein the first clutch and thefirst brake are operated at a first forward speed, the first clutch andthe second brake are operated at a second forward speed, the firstclutch and the second clutch are operated at a third forward speed, thefirst clutch and the third clutch are operated at a fourth forwardspeed, the second clutch and the third clutch are operated at a fifthforward speed, the third clutch and the second brake are operated at asixth forward speed, the third clutch and the fourth clutch are operatedat a seventh forward speed, the fourth clutch and the second brake areoperated at an eighth forward speed, the second clutch and the fourthclutch are operated at a ninth forward speed, and the second clutch andthe first brake are operated at a reverse speed.
 6. The planetary geartrain of claim 2, wherein the frictional elements comprise: a firstclutch selectively connecting the third transfer gear with the sixthrotation element; a second clutch selectively connecting the input shaftwith the first rotation element; a third clutch selectively connectingthe second rotation element with the input shaft and the fourth transfergear; a fourth clutch selectively connecting the fourth transfer gearwith the sixth rotation element; a first brake selectively connectingthe second rotation element with the transmission housing; and a secondbrake selectively connecting the first rotation element with thetransmission housing.
 7. The planetary gear train of claim 2, whereinthe frictional elements comprise: a first clutch selectively connectingthe third transfer gear with the sixth rotation element; a second clutchselectively connecting the input shaft with the first rotation element;a third clutch selectively connecting the second rotation element withthe third transfer gear; a fourth clutch selectively connecting theinput shaft with the fourth transfer gear; a first brake selectivelyconnecting the fourth rotation element with the transmission housing;and a second brake selectively connecting the first rotation elementwith the transmission housing.
 8. The planetary gear train of claim 2,wherein the frictional elements comprise: a first clutch selectivelyconnecting the input shaft with the third transfer gear; a second clutchselectively connecting the input shaft with the first rotation element;a third clutch selectively connecting the second rotation element withthe input shaft and the fourth transfer gear; a fourth clutchselectively connecting the fourth transfer gear with the sixth rotationelement; a first brake selectively connecting the fourth rotationelement with the transmission housing; and a second brake selectivelyconnecting the first rotation element with the transmission housing. 9.A planetary gear train of an automatic transmission for a vehicle,comprising: an input shaft receiving torque of an engine; an outputshaft disposed in parallel with the input shaft at a predetermineddistance from the input shaft and outputting changed torque; a firstplanetary gear set disposed on the input shaft and including a firstrotation element selectively connected to the input shaft andselectively operated as a fixed element, a second rotation elementselectively connected to the input shaft, and a third rotation element;a second planetary gear set disposed on the output shaft, and includinga fourth rotation element connected to the second rotation element andselectively operated as a fixed element, a fifth rotation elementconnected to the third rotation element and directly connected to theoutput shaft, and a sixth rotation element selectively connected to theinput shaft through two externally-meshed gears, wherein a gear ratio ofone of the two externally-meshed gears is different from that of theother of the two externally-meshed gears; a first transfer gearconnecting the second rotation element with the fourth rotation element;a second transfer gear connecting the third rotation element with thefifth rotation element; a third transfer gear connecting the input shaftwith the sixth rotation element; a fourth transfer gear connecting theinput shaft with the sixth rotation element; and frictional elementsincluding clutches connecting the input shaft and the rotation elementsof the first and second planetary gear sets and brakes connecting therotation elements of the first and second planetary gear sets and atransmission housing, wherein the first planetary gear set is a singlepinion planetary gear set including a first sun gear being the firstrotation element, a first planet carrier being the second rotationelement, and a first ring gear being the third rotation element, and thesecond planetary gear set is a single pinion planetary gear set andincluding a second sun gear being the fourth rotation element, a secondplanet carrier being the fifth rotation element, and a second ring gearbeing the sixth rotation element.
 10. The planetary gear train of claim9, wherein a gear ratio of the third transfer gear is different fromthat of the fourth transfer gear.
 11. The planetary gear train of claim9, wherein the frictional elements comprise: a first clutch selectivelyconnecting the third transfer gear with the sixth rotation element; asecond clutch selectively connecting the input shaft with the firstrotation element; a third clutch selectively connecting the secondrotation element with the input shaft and the fourth transfer gear; afourth clutch selectively connecting the fourth transfer gear with thesixth rotation element; a first brake selectively connecting the fourthrotation element with the transmission housing; and a second brakeselectively connecting the first rotation element with the transmissionhousing.
 12. The planetary gear train of claim 9, wherein the frictionalelements comprise: a first clutch selectively connecting the thirdtransfer gear with the sixth rotation element; a second clutchselectively connecting the input shaft with the first rotation element;a third clutch selectively connecting the second rotation element withthe input shaft and the fourth transfer gear; a fourth clutchselectively connecting the fourth transfer gear with the sixth rotationelement; a first brake selectively connecting the second rotationelement with the transmission housing; and a second brake selectivelyconnecting the first rotation element with the transmission housing. 13.The planetary gear train of claim 9, wherein the frictional elementscomprise: a first clutch selectively connecting the third transfer gearwith the sixth rotation element; a second clutch selectively connectingthe input shaft with the first rotation element; a third clutchselectively connecting the second rotation element with the fourthtransfer gear; a fourth clutch selectively connecting the input shaftwith the fourth transfer gear; a first brake selectively connecting thefourth rotation element with the transmission housing; and a secondbrake selectively connecting the first rotation element with thetransmission housing.
 14. The planetary gear train of claim 9, whereinthe frictional elements comprise: a first clutch selectively connectingthe input shaft with the third transfer gear; a second clutchselectively connecting the input shaft with the first rotation element;a third clutch selectively connecting the second rotation element withthe input shaft and the fourth transfer gear; a fourth clutchselectively connecting the fourth transfer gear with the sixth rotationelement; a first brake selectively connecting the fourth rotationelement with the transmission housing; and a second brake selectivelyconnecting the first rotation element with the transmission housing. 15.A planetary gear train of an automatic transmission for a vehicle,comprising: an input shaft receiving torque of an engine; an outputshaft disposed in parallel with the input shaft at a predetermineddistance from the input shaft and outputting changed torque; a firstplanetary gear set disposed on the input shaft and including a firstrotation element selectively connected to the input shaft andselectively operated as a fixed element, a second rotation elementselectively connected to the input shaft, and a third rotation element;a second planetary gear set disposed on the output shaft, and includinga fourth rotation element connected to the second rotation element andselectively operated as a fixed element, a fifth rotation elementconnected to the third rotation element and directly connected to theoutput shaft, and a sixth rotation element selectively connected to theinput shaft through two externally-meshed gears, wherein a gear ratio ofone of the two externally-meshed gears is different from that of theother of the two externally-meshed gears; a first transfer gearconnecting the second rotation element with the fourth rotation element;a second transfer gear connecting the third rotation element with thefifth rotation element; a third transfer gear connecting the input shaftwith the sixth rotation element; a fourth transfer gear connecting theinput shaft with the sixth rotation element; and frictional elementsincluding clutches connecting the input shaft and the rotation elementsof the first and second planetary gear sets and brakes connecting therotation elements of the first and second planetary gear sets and atransmission housing, wherein the frictional elements comprise: a firstclutch selectively connecting the third transfer gear with the sixthrotation element; a second clutch selectively connecting the input shaftwith the first rotation element; a third clutch selectively connectingthe second rotation element with the input shaft and the fourth transfergear; a fourth clutch selectively connecting the fourth transfer gearwith the sixth rotation element; a first brake selectively connectingthe fourth rotation element with the transmission housing; and a secondbrake selectively connecting the first rotation element with thetransmission housing.